Partial Discharge Measurements on Dibenzyltoluene for High Temperature Encapsulant Application up to 350°C

Partial discharges characterization on ceramic substrates and dielectric liquids under high temperature up to $350^{\circ}\mathrm{C}$ is investigated. Aluminum nitride (AlN) and alumina (Al 2 O 3 substrates, and a high temperature non-polar dibenzyltoluene (DBT) liquid are used. Several complementary measurements are also done in a synthetic ester liquid. PD measurements on AlN substrates embedded in DBT show a good behavior up to $300^{\circ}\mathrm{C}$, and up to $350^{\circ}\mathrm{C}$ with Alumina. This shows that high temperature insulating liquid may constitute a good alternative to silicone gels for the encapsulation of power electronics circuits at high temperature and high voltage. The comparison between PD characteristics in the liquid alone and with substrates show that PDs mostly occur within the ceramic material at temperatures up to $300^{\circ}\mathrm{C}$.